sha256 based on different outcomes -

is posible know $server_seed value based on different outcomes of code?

$server_seed = "**4799e37e2f397e6196813367a11042335521f8d2**"; (unknown value)  $round_id = 73904; (known value);  $round_date = "2016-01-23-11-59-37"; (known value)  $hash = hash("sha256", $server_seed . "-" . $round_id . "-" . $round_date);  $roll = bcmod(hexdec(substr($hash, 0, 8)), 15);  echo $roll; 

the code gives value betwen 0 , 14 every time $round_id increases 1 , $round_date increased 45 seconds. have access tons of different outcomes , know $round_id , $round_date, $server_seed unknown (is same lenght).

my question if there way know $server_seed value using different outcomes, making code checks different $server_seeds values , tells values give outcomes inserted.

is there anyway $server_seed value in easy , simple way?

there no simple way. sha256 cryptographic hash function , satisfies definition of such function:

a cryptographic hash function hash function considered practically impossible invert.

presently no successful attacks have been reported on sha-2

as other answer notes, brute-force attack possible unfeasible perform @ current state of existing computing technologies , hardware.